Plate-like optical storage medium and reading device

ABSTRACT

An optical storage medium and a reading device are proposed, wherein the optical storage medium has the format of a credit card.

BACKGROUND OF THE INVENTION

The invention is based on a plate-shaped, optical storage medium andreading device.

A plate-shaped, optical storage medium has been disclosed by GermanPatent Document 4311683. These storage mediums which are generallyreferred to as CDs (compact disc) contain binary data which are storedserially in a sequence of heights and depths along a spiral track. TheCD is embodied as a round disc upon which the spiral track goes from theinside to the outside. For scanning, the disc is set into a circularrotational motion, wherein in order to achieve a constant data flowdensity, the rotation speed decreases during a scan from the insidetoward the outside.

A CD reading device has been disclosed, for example, by GermanDisclosure Document 4225727. In order to scan the CD, the laser diode,whose light is reflected on the surface of the CD, is moved radiallyover the CD which is rotating at different speeds.

EP-A-0 666 565 has disclosed a reading device for reading an opticalcard, which includes an optical reading head with a laser diode andoptical lenses for focusing the laser beam. The optical reading headalso includes an optical sensor for detecting the reflected laser beam.The optical card rests on a spacer ring, which assures a certaindistance between the objective lenses of a rotary plate and the opticalcard. The rotary plate with the objective lenses of the scanning head isset into rotation in order to optically scan the optical card.

U.S. Pat. No. 4,656,346 has disclosed an optical system for reading anoptical card in credit card format. The optical system includes a laserlight source, which emits a laser beam that passes through focusingoptics. Furthermore, there are known detectors which detect the laserbeam that is held by movable retention device. The laser beams followthe tracks of the optical storage card by virtue of the fact that theretention device is moved in the longitudinal direction of the card inrelation to the laser beams.

SUMMARY OF THE INVENTION

The plate-shaped, optical storage medium according to the invention hasthe advantage over the prior art that it has a small, convenient format,which has the shape and size of a standard card according to ISO 7810.The optical storage medium according to the invention provides a smallexchangeable storage medium which can be inexpensively manufactured andis not sensitive to environmental influences. Therefore primarily, itcan be used very easily in mobile devices, for example in a motorvehicle. It is particularly advantageous that despite the smalldimensions of the storage medium, a large quantity of data can bestored.

An advantageous improvement and update of the storage medium is possibleby means of the measures taken in the dependent claims. The storagevolume can be advantageously doubled by using both sides of the storagemedium.

The data are written along tracks which are disposed either parallel orperpendicular to the longitudinal axis of the card. As a result, thedata can be read without the card according to the invention having tobe set into rotation in the reading device as was previously the casewith conventional storage plates.

The reading device according to the invention for reading theplate-shaped, optical storage medium in the standard card formatadvantageously has a suitable opening for receiving the optical storagemedium as well as at least one laser diode for reading the data. Thereading device does not require a motor that sets the optical storagemedium into a rotating motion and does not require a movable scanninghead which moves really over the surface of the storage medium. Thereading device consequently has significantly fewer components sincemovements of the storage medium itself are eliminated.

The reading device advantageously has at least one laser diode, whoselight follows the track of the storage medium. It is advantageous thatfor a very rapid reading potential, a laser array is installed in whicha number of laser diodes simultaneously emit light and can detect databy using the interference process.

Advantageously, the beam of the laser diode follows the track of thestorage medium by means of an optical device wherein this device can bea movable mirror or an electrooptical component.

In another embodiment of the reading device, a mechanical movement ofthe scanning head in the plane over the storage plate is advantageous inorder to prevent a large deflection angle of the beam away from theperpendicular to the storage surface.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is represented in the drawingsand will be explained in detail in the subsequent description.

FIG. 1 shows an optical storage medium according to the invention with areading unit,

FIG. 2 shows a reading device with a laser diode array, and

FIG. 3 shows an embodiment of the reading device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the plate-shaped storage medium 1 according to theinvention, which has the format and size of standard cards according toISO 7810. It is written with binary data along the track 6. The readingdevice 10 according to the invention has a scanning head 12 with a laser2, a focusing unit 3, a deflection unit 8, and a receiving unit 4. Thedecoder 11 is connected to the scanning head 12 by way of the signaloutput 13. The laser beam 5 is reflected against the surface of thestorage medium 1 into the beam 9 and is projected onto the receivingunit.

The storage medium 1 that is embodied as a storage card has a smooth,optical surface, upon which digital data are stored serially by means ofa sequence of heights and depths. In the example of FIG. 1, the datatracks 6 are disposed perpendicular to the card longitudinal axis. Thedisposition of the data lines can also be carried out parallel to thecard longitudinal axis. In a first exemplary embodiment, the scanning ofthe data lines 6 is executed by a respective placement of the laser beam5 on the card edge. The laser beam 5 is guided diagonally 7 between theend point of the currently read track and the beginning point of thenext track to be read. No data is recorded in the line return 7. Theprovision is also made that the scanning takes place by way of acontinuous motion along the lines with a stroke into the next line,without the reading process having to be stopped. The scanning head 12emits the laser beam 5, which is first focused onto the surface of thestorage plate by the. focusing unit 3. The deflection unit 8, which canfor example contain a number of mirrors, is connected in order to causethe beam follow the track on the storage card. In the scanning of anoptical card of the size of a credit card, excessive deflection anglesof the beam away from the perpendicular to the storage surface do notoccur. As a result, other suitable optical components can also be usedfor deflecting the laser beam or for focusing and deflecting. Thereflected beam is received and evaluated in the detector 4. The signal13 is supplied to the decoder 11, which decodes the digital data andprepares it for further processing.

If the storage density of known CDs is used as a basis, high storagedensities of up to 260 MB can be achieved with the storage cardaccording to the invention. The storage medium can be used for variousportable devices.

FIG. 2 shows the storage card 1 with the tracks 6 of binary data. Thescanning head 12 includes a laser diode array 14, which emits laserbeams 5.

If the intent is to reduce the access time for reading the optical cardaccording to the invention, it is possible to use a number of laserdiodes in the form of a laser diode array 14. Each beam 5 of a diode isfocused on a respective track 6 of the card 1 and is only deflectedalong this track in the arrow direction. This eliminates deflectionunits that have to deflect the laser beam by a large angle and intwo-dimensional fashion. The reading of data can therefore also occur inparallel fashion, when the further processing is assured.

If the evaluation of the data of the storage medium should be impairedby the attendant acute angle of the laser beam in relation to thesurface, the scanning head 12 can be moved two-dimensionally over thecard-shaped storage medium. However, this requires an additionalmechanical expenditure in the reading device.

FIG. 3 shows a reading device 10 for the optical storage card 1. It hasan opening 15 and a receptacle 16. The stop 17 is installed on thehousing. The scanning head 12 emits data by way of the signal output 13.The storage medium 1 is inserted into the opening 15 of the readingdevice. A suitable mechanism must receive and fix the storage card thereso that a definite distance is assured between the surface of thestorage medium 1 and the scanning head 12. A variety of knownembodiments can be used for this which are already known from chip cardreading devices. For example, the storage card 1 is received by areceptacle 16 in the reading device. This receptacle 16 moves upwarduntil reaching a stop 17. In this position, the storage card is fixed inrelation to the scanning head. In order to withdraw the card 1, thereceptacle is lowered and an eject mechanism is used, as is also knownfrom chip card reading devices.

What is claimed is:
 1. A reading device for reading a plate-shapedoptical storage medium, the reading device comprising means forming anopening for receiving a storage medium; a scanning head with a laserdiode for scanning an optical surface of the storage medium; focusingmeans for focusing a laser beam emitted by said scanning head onto thesurface of the storage medium; a detector for detecting a reflectedlaser beam, said opening being formed so as to receive the storagemedium in credit card format, so that the storage medium is secured at adefinite distance from said scanning head; and an optical deflectiondevice which causes the laser beam emitted by said scanning head tofollow a track of the storage medium, while said optical storage mediumand said scanning head are immovable.
 2. A reading device as defined inclaim 1, wherein said optical deflection device is formed so as to causethe laser beam of the laser diode to follow the track of the storagemedium.
 3. A reading device as defined in claim 1, wherein said opticaldeflection device has at least one movable mirror which causes the laserbeam of the laser diode to follow the track of the storage medium.
 4. Areading device as defined in claim 1, wherein said optical deflectiondevice includes at least one electro optical component which causes thelaser beam of the laser diode to follow the track of the storage medium.